In order to improve the processing efficiency of a machine tool, the machine tool is required to be able to feed its mobile body such as a table, a saddle or the like at high speed. In the case where the machine tool is constructed to include sliding surfaces on the mobile body, when the mobile body is fed at high speed, frictional heat is generated by the friction of the sliding surfaces. Therefore, a problem arises that, when the frictional heat is transferred to various parts, thermal deformation of the mobile body occurs, the processing precision of the machine tool is degraded.
A method for removing the heat generated by the friction of sliding surfaces of a bed or a saddle of a machine tool has been disclosed in Japanese Patent Publication No. 2000-117571. In this method, pipelines are provided in the rib of the bed sliding surface or under the saddle sliding surface, and a coolant liquid is circulated through the pipelines so as to suppress a temperature rise in the bed sliding surfaces or the saddle sliding surfaces.
Further, a method for supplying a coolant liquid in order to cool various portions of a machine tool while adjusting the flow rate of the coolant liquid in response to the amount of heat generated in various portions to obtain uniform temperature at various portions of the machine tool is disclosed in Japanese Patent Publication No. 2002-166337. In this method, a pipeline for supplying the coolant liquid is provided on each heat generating portion of the machine tool and a valve for adjusting the flow rate of the coolant liquid is provided in each pipeline so that the flow rate of the coolant liquid can be adjusted in response to the amount of heat generated at each portion of the machine tool so as to suppress temperature fluctuation in various portions of the machine.
The cooling device of a machine tool as disclosed in the above-described Japanese Patent Publication No. 2000-117571 and Japanese Patent Publication No. 2002-166337 has temperature sensors embedded in various portions of the machine in order to detect temperature in various portions of the machine or temperature differences between various portions of the machine. Thus, the temperature or flow rate of the coolant is adjusted in response to the detected temperature of various portions, and the coolant liquid is circulated so that heat generated in various portions of the machine can be reduced and temperature fluctuation in various portions of the machine can be suppressed. Therefore, there is a problem that a large number of sensors and flow rate adjusting means are required which results in an expensive machine.